BRITISH TELEVISION HAS JUST SCREENED a new Easter Island documentary from BBC's "Horizon" stable, which had already made a double-program on the subject more than ten years ago. When I was first contacted by the new program makers, I was told that (a) they wanted to focus on the new work and new ideas that have arisen in the intervening years, and (b) in particular they wanted to assess three conflicting theories about the island's downfall - i.e. the manmade ecological disaster model, the natural ecological disaster model, and the theory that it was European impact which caused all the trouble. What we get in the finished show, however, is somewhat different from these early intentions.</p